Electrode construction for electroluminescent tubes



Sept. 25, 1934.

R. R. WILEY ET AL ELECTRODE CONSTRUCTION FOR ELECTROLUMINESCENT TUBES Filed Nov. 17, 1928 Ro R wa aifirdl J .Bmndi Patented Sept. 25, 1934 NlTE-D STA TFES .ELECTRODE LCONSTRUCTION .FOB, IELEC- TROLUMINESGENT TUBES jRoy It. Wiley and Alfred L. Brandt, Bufialo,

'N."Y,, assignors to Flexlume Corporation, Tonawanda, N. -Y. a corporation-of New York ApplicationNovember 17, 1928; Serial No. 3205150 :1 Claim. (Cl. 176'126) This invention relates in a generalwayto electroluminescent tubes which employ an inert gas such as neon asthe luminescent medium andmore tpagticularly to the electrode construction of the u es.

The principal object of the invention is a construction in-whichprovision is made for protect- -ing those portions of the lead-in wires in the vicinity of the electrodes against the disintegrat- "ing actionof theelectriccurrent which is utilized to energize the tubes.

Embodiments of the invention are illustrated in theaccompanying-drawing, wherein:

Figure 1 is alongitudinal sectional view of the electrode construction in relati'on to theterminal portion of-a tube;

Figure 2 is a section along-line 22 of Figure 1. Figure3 is a longitudinalsectional' view similar to Figure 1 showing a modified form of construction.

i 1 Figure 4 is a section along line 4-4 of Figure 3. Thetube 1 is sufficiently indicatedbyshowing the terminal portion thereof in which the reentrant flare is provided with-a-glass seal 2 through which the lead-in wire 3 passes. The electrode 4 to'which the lead-in wire is connected maybe composed of any suitable materialand fashioned inany suitable iorm. Preferably it is composed of copper of 'foraminous structure and arranged theiorm of a cylinder;

The electrode 4 is arrangedwithin a'chamber provided by a hollow member*5 of glass or other suitable insulating material which, may be of any suitable form and supportedin any suitable manner. A s shown and preferred,thehollowinemher is made. of cylindrical shape having the end' through which the lead-in wire passes, closed-as at .6. The electrode is preferably although not necessarily anchored in the hollow member. This ma bea om l hs brh nsih hqllqwm r ber so "as to cause it -to flow "into and fill 'the 'forarnina-in the electrode, leaving a suitable; area of thelatter exposed as anactive area. while the anchorage of the electrode in thismanner considerably decreases the j electrode surface otherwise available as an active area, this reduction of active surface in no way impairs the operation-of thetube.

The hollow member is axially located within the tube, preferably by an axially disposed glass cylinder 7, the opposite ends of which are'provided with annular supporting flanges 8 of a diameter substantially equal to the inside diameter of the tube, the hollow member being thereby substantially spaced concentrically from the wall from the axial center of the tube.

of the tube with resultant thermaland electrical insulation from said wall. The supporting flanges 8 also function to reduce the area of the gas-path extending along the outer face of the cylinder '7 and thereby increase the electrical resistance of such path-t0 an extent such as to prevent any electrical discharge action from taking place around the axially located uninsulated portion 3a of the lead in wire 3 between the glass seal 2 and the hollow member 5. In this conmotion, it should be noted that when any uninsulated portion-of theElead-in wire 3 is permitted to extend along the axial center of a tube with a comparatively low resistance gas'path connecting the lead-in wire, rendering the tube inoperative. While it can beavoided by increasing the electrical resistance of the connecting path as indil5 cated above and also by insulating the lead-in wire from the connecting path, wehave observed that it is effectively prevented by the simple expedient of substantially ofisetting the lead-in wire This last menso tioned method is utilized to protect that portion of the lead-in wire extending within the electrode chamber, such portion being: substantially offset.

' From the construction thus-far described, it is evident that the active area of the electrodeof the current flowing through the tube is compelled to flow into and/or out of theelectrode chamber. Withtthis in mind it may .be pointed 'out'that the present invention is concerned mainly with the communication between the electrod chamber and thetube proper.

Generally stated, the invention consists in re- 35 stricting or obstructing the communication between the electrode chamber and the tube proper. The nature of the action which takes place as a result of this type of construction is not, at this-time, fully understood but its'beneficial effects-are apparent. One surprising feature resulting from this constructionfls the very great decrease in theefiective rate at which the volatilized metal is deposited. Whether or not this result is due to a decrease in the rate of volatilization or to the revolatilization of the deposited metal, has not yet been determined. Whatever the cause, it may be said that the rate at which the deposit accumulates, decreases as the communication is relatively more restricted or ob- 1.10

structed while the amount of such deposit is comparatively small under all conditions of operation.

A further effect resulting from this construction is the decrease in the tendency of the deposit to creep along the wall of the hollow member. So far as we have been able to determine, any restriction, however slight, will, to some extent at least, effect a decrease in the tendency of the deposit to creep but will not, necessarily, overcome such tendency. There seems to be a critical value of restriction below which the deposit will creep more or less, and above which it is entirely confined within the hollow member even though the current values be increased several times in excess of their normal operating rating. In other words, the greater the restriction within the limit of practicability the better the result. It is apparent that such metal as is detached from the body of the electrode and confined within the hollow member, will be maintained at a relatively high temperature so that the rate at which the inert gas is occluded is very materially reduced. Furthermore, it is evident that the con finernent of the deposit to the electrode chamber favors the re-uniting oi the deposit with the electrode whereby the life of the latter is indefinitely prolonged.

As a result of the features noted, we have found that the electrode can be made extremely small and operated at a relatively high temperature without any danger of the electrode disintegrating or being, consumed and with a rate of gas-occlusion which is so small as to be negligible, the result being that a tube in which the present invention is utilized will have an effective life several times greater than that of tubes heretofore used.

' 9. In this construction it is obvious that the value of the obstruction aiiorded by the passage 9 can be increased by further reducing its diameter and/or increasing its length. It is equally obvious that a decrease in the diameter of the passage or an increase inits length will effect an increase in its electrical resistance. Hence .While the beneficial efjects noted continually improve as the communication is more and more obstructed, the extent to which the obstruction can be carried out is limited. by the increase in the electrical resistance of the communication. In other words, the beneficial effects improve as the communication resistance is increased; hence the latter factor places a practical limit upon the extent to which the obstruction can be carried out.

The opening or passage 9 should in any case be less in diameter than the minimum diameter of the electrode 4:; whereby the electrode is removed from the direct eiiect of the intensely active axially located column of gas within and adjacent the ends of the passage 9. Very good results, superior in degree to constructions heretofore used, have been obtained, for example, with a tube of 19 millimeters diameter having a neon pressure of 8 to 10 millimeters of mercury, a hollow member of the form shown in Figure 1 having a maximum inside diameter of 5 millimeters with a restricted passage 9 of 3 millimeters diameter and about 3 millimeters length and an electrode 4 enclosed within the hollow member and having a length of 10 millimeters and a minimum diameter of 4 to 4 millimeters, the operating current having a value of approximately 25 milliamperes. Of course, the proportions of the parts may be varied indefinitely while utilizing the principles and obtaining the benefits of the invention as herein pointed out. It will, of course, be understood that the tube is initially prepared in the usual manner and it is noted that the electrode despite its small size, very effectively carries and withstands the heavy preliminary bombarding currents.

The means by which the communication between the electrode chamber and the interior of the tube proper is restricted or obstructed may take various forms. In Figures 3 and 4, we have shown a different construction for accomplishing the same result. In this construction, the hollow member 5 is in the form of a cylinder of uniform bore from its closed end to its open end. The open end is, however, covered by a cap 10 which is secured to the hollow member. The cap is of such form as to definean annular passage 9a extending from the open end of the hollowmember around its adjacent edge and rearwardly along its outer surface to a series of apertures 11 formed in the cap and through which communication with the tube proper is established. The lead-in Wire 3 in this construction, is protected and the hollow member 5 supported by a glass sleeve 12 which extends inwardly of the tube from the glass seal 2.

- Strictly speaking, if the term restricted be regarded as contemplating an aspect of relative size, the communication illustrated in Figures 3 and 4= is obstructed rather than restricted but the results seem to be the same. Since the restriction of a communication has an aspect of obstruction, it may be noted that both forms may be generically regarded as obstructed communications between the electrode chamber and the tube wherein the electrode is removed or remote from the direct effects of the column of gas within and adjacent the ends of the obstructed passage.

Having fully described our invention, we claim:

An electrode construction for electroluminescent tubes comprising in combination with such a tube, a body arranged within said tube and formed with an electrode chamber, an electrode arranged along the wall of said chamber and a lead-in wire extending through a wall of said chamber into the same, said lead-in Wire being connected to the electrode and having that portionextending into the electrode chamber substantially oiiset from. the axial center of the tube, thereby being protected from direct exposure to the axial center of discharge.

ROY R. WILEY. ALFRED L. BRANDT. 

